dereferencing null

[Jacob Carlborg]

On 2012-03-05 07:25, Walter Bright wrote:
> On 3/4/2012 6:31 PM, Chad J wrote:
>> class Bar
>> {
>> int foo;
>> }
>>
>> void main()
>> {
>> Bar bar;
>> try {
>> bar.foo = 5;
>> } catch ( Exception e ) {
>> writefln("%s",e);
>> }
>> }
>>
>> DMD 2.057 on Gentoo Linux, compiled with "-g -debug". It prints this:
>> Segmentation fault
>>
>> Very frustrating!
>
> This is what I get (I added in an import std.stdio;):
>
> dmd foo -gc
> gdb foo
> GNU gdb (GDB) 7.2-ubuntu
> Copyright (C) 2010 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later
> <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from /home/walter/cbx/mars/foo...done.
> (gdb) run
> Starting program: /home/walter/cbx/mars/foo
> [Thread debugging using libthread_db enabled]
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000000000401e45 in D main () at foo.d:13
> 13 bar.foo = 5;
> (gdb) bt
> #0 0x0000000000401e45 in D main () at foo.d:13
> #1 0x000000000040aa9b in rt.dmain2.main() ()
> #2 0x0000000000636010 in ?? ()
> #3 0x00007ffff7fdeae0 in ?? ()
> #4 0x00007fffffffeb30 in ?? ()
> #5 0x00007fffffffea00 in ?? ()
> #6 0x000000000040a41b in rt.dmain2.main() ()
> #7 0x0000000000000001 in ?? ()
> #8 0x0000000000000019 in ?? ()
> #9 0x0000000000636020 in ?? ()
> #10 0x00007fffffffeb30 in ?? ()
> #11 0x00007ffff7ffe4c0 in ?? ()
> #12 0x00007fffffffe8b0 in ?? ()
> #13 0x00007fffffffeb30 in ?? ()
> #14 0x00007fffffffea30 in ?? ()
> #15 0x000000000040aaee in rt.dmain2.main() ()
> #16 0x000000000040aa84 in rt.dmain2.main() ()
> #17 0x00007fffffffeb30 in ?? ()
> #18 0x00007fffffffea80 in ?? ()
> #19 0x000000000040a41b in rt.dmain2.main() ()
> #20 0x0000000000000001 in ?? ()
> #21 0x0000000000000019 in ?? ()
> #22 0x0000000000636020 in ?? ()
> #23 0x0000000000000001 in ?? ()
> #24 0x0000000000636020 in ?? ()
> #25 0x00007fffffffee01 in ?? ()
> #26 0x00007fffffffeb30 in ?? ()
> #27 0x00007fffffffeb30 in ?? ()
> #28 0x000000000040a3b3 in main ()
> (gdb)
>
> By running it under gdb (the debugger), it tells me what file and line
> it failed on, and gives a lovely stack trace.
>
> There really are only 3 gdb commands you need (and the only ones I
> remember):
>
> run (run your program)
> bt (print a backtrace)
> quit (exit gdb)
>
> Voila!
>
> Also, a null pointer exception is only one of a whole menagerie of
> possible hardware-detected errors. There's a limit on the compiler
> instrumenting code to detect these. At some point, it really is worth
> learning how to use the debugger.

Is demangling supposed to work on Mac OS X?

-- 
/Jacob Carlborg